A scroll compressor comprises two disk-like end plates, each having a spiral wrap at one side thereof, facing each other. The two wraps are in contact along several contact lines, forming a plurality of compressor chambers therebetween. In the scroll compressor, one end plate revolves around the other stationary end plate in an eccentric orbit, so that the contact lines gradually shift from the outer circumference toward the inner circumference. The gas that is drawn into the compression chambers between the two wraps is gradually compressed from the outer circumference toward the inner circumference.
There are basically two types of scroll compressor: a lower pressure type, in which the inside of the vessel is maintained at lower pressure, as in U.S. Pat. Nos. 3,011,694 and 4,065,279, and a higher pressure type, in which there is a higher pressure chamber on the opposite side to the compression chamber of the orbiting end plate, as in U.S. Pat. Nos. 3,884,599 and 3,994,633.
In general, in a higher pressure type scroll compressor, a rotation drive device such as a motor and a compression device to compress the gas are installed inside a sealed vessel. The gas (such as air) to be compressed passes through a guide tube which is inserted into the sealed vessel, and enters the compression chamber from one or more inlets on the outer circumference of the compressor. After the compressed gas at a high pressure from the compression chamber has passed through each part of the interior of the sealed vessel, it is exhausted out of the sealed vessel to the outside. Consequently, since the entire sealed vessel is heated by the heat generated when the gas is compressed, if the path of the drawn gas is long from its inlet or suction through the sealed vessel to the compression chambers, then the drawn gas will be heated. Also, the high pressure inside the sealed vessel acts on the first surface or rear surface of the orbiting end plate, that is, the surface away from the compression chambers, and a strong force presses against the stationary end plate, causing a large friction force to occur between the two end plates so that the drawn-in gas is heated. When the gas drawn in from the suction port is thus heated before it enters the compression chambers, the exhaust mass flow is reduced, thus reducing the compressor capacity.
In addition, in existing modes of scroll compressor, there is another problem as well; gas is always being drawn in so that the part of the gas which misses the timing of the compression cycle accumulates inside the compression section, whereas, when a gas suction port is located near the scroll wrap to make the gas suction intermittent, there is the limitation that the diameter of the gas suction port cannot be made larger than the material thickness of the wrap, so the resistance in the flow path cannot be made small.
The concept of liquid injection, in which cooled liquid passes through the stationary end plate into a compression chamber between the end plates, has already been suggested in the prior art, but the existing technology does not suggest that the gas to be compressed is fed through the stationary end plate.